Prepare thyselves, travelers. Starting Friday night, lane and ramp closures will occur on westbound Interstate 90 between Bellevue and Mercer Island for an entire week, constricting the thoroughfare down to one lane at the height of the closures.

Like a clogged artery, the effects are expected to be felt throughout the Seattle region, with some reports warning of 10-mile backups and advising adding an hour to the commute time.

Furthermore, President Barack Obama is expected to visit the area on Tuesday. His motorcade will probably pile on more road closures. Oh, boy!

The I-90 closures will occur so crews can repair expansion joints on the East Channel Bridge, which connects Mercer Island to Bellevue. The first ramp will close about 8 a.m. Friday, followed by additional various ramp and lane closures by the day. Detours will also be established for people who live and travel through the area. The freeway is expected to return to normalcy about 5 a.m. Friday, July 25. Find detailed descriptions of the closures at the WSDOT website.

WSDOT traffic engineers predict it will take motorists at least an hour to travel from Issaquah to Seattle on I-90 – if 60 percent of the usual I-90 commuters use a different route, alternate transportation or stay away.

The Washington State Transportation Commission, which makes tolling decisions, has opted not to reduce or eliminate its tolling fees on the state Route 520 bridge, which will be a natural alternative for people needing to get to the west side of Lake Washington.

“To divert from (the usual tolling) plan would be detrimental to the state’s financial standing and the financing of the new SR 520 Bridge,” the agency said in a statement, adding that a week-long tolling exemption would cost the state $1.3 million.

The statement goes on:

“For every free ride given means the lost revenue will have to be made up at a later date by drivers using the SR 520 Bridge. So essentially the regular, day-to-day users of SR 520 will end up subsidizing the ‘free pass’ I-90 users are seeking, due to the traffic impacts of next week’s construction project. Given there are other free alternative routes available, this approach does not seem reasonable nor prudent.”

As for Obama’s fundraising trip, details haven’t yet emerged on the timing or location of the resulting road closures expected to occur.

Hey, at least you can take it easy on your car’s AC. The National Weather Service forecasts highs in the 70s with a chance of showers for the next few days – more mild than the past week’s heat.